Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$177.88	11.183%	$197.7723	$197.77	$197.75	$197.80
Purchase #2	$163.42	13.285%	$185.1303	$185.13	$185.15	$185.10
Purchase #3	$82.34	8.725%	$89.5242	$89.52	$89.50	$89.50
Purchase #4	$76.38	7.445%	$82.0665	$82.07	$82.05	$82.10
Purchase #5	$150.51	5.251%	$158.4133	$158.41	$158.40	$158.40
Purchase #6	$94.51	9.459%	$103.4497	$103.45	$103.45	$103.40
Purchase #7	$43.96	7.523%	$47.2671	$47.27	$47.25	$47.30
7 purchase totals =	$789.00		$863.6234	$863.62	$863.55	$863.60